The invention departs from the problem that when articles are conveyed on a band-type conveyor and these articles are subjected to an acceleration, be it by acceleration of the band conveyor itself or by an acceleration imparted on the articles on the band-type conveyor by an additional drive, e.g. by imparting to the articles a spinning acceleration around a rotational axis, that then the articles will become misaligned on the band-type conveyor, e.g. due to reacting forces of inertia. By using such band-type conveyors to convey the articles, e.g. in a working or treating unit, it is often of high importance to have each of the articles arriving at such a station in an exactly predetermined position and positional relationship with respect to the next following article.
From U.S. Pat. No. 3,310,431 there is known a method to convey electrical components of cylindrical form with laterally extending wire tips on a band-type conveyor, particularly a chain conveyor wherein the wire tips are held in U-shaped bearings laterally arranged on the conveyor. The U-shaped bearings permit a spinning movement of the components around their axis during their conveyance. Before the components are fed to a coating station, their laterally extending wires are squeezed between two laterally spaced endless bands, laterally distant from the U-shaped bearings, and accordingly positioned stationary support surfaces. Thus, a spinning action is imposed on the electric components which arrive, spinning around their axis, at the coating station. This known method is disadvantageous in that a component, as an article to be conveyed, is squeezed laterally distant from the surface defined by the band-type conveyor, so that two equivalent squeezing arrangements must be provided on both sides of the band-type conveyor.
An object of the present invention is to provide a method of the above mentioned type which avoids the said disadvantage of the prior art method, and to provide apparatus for performing the method where the apparatus has a significantly simplified construction for realization of the method.
This object is accomplished by the method of the invention for preventing articles from becoming misaligned as conveyed in a band-type conveyor and subjected to an acceleration along the conveyance path, the method comprising squeezing the articles between the band-type conveyor and a squeezing arrangement at least at a location along the path, opposite the band-type conveyor and within an area defined by the width of the band-type conveyor. If there is a need, when conveying cylindrical articles, to impart to the articles a rotational spin during their conveyance on the band-type conveyor, it is proposed to perform the inventive method by rotatably supporting the articles for rotation around their axis, at predetermined positions on the bank-type conveyor and operating the squeezing means and the band-type conveyor with a speed difference so as to subject the articles to spinning around their axis.
Instead of separately providing a drive arrangement for subjecting the articles to a spinning drive, as e.g. known from the Japanese publication no. 46-32352, the inventively arranged squeezing means are simultaneously used to in fact provide for the spinning drive for the articles. As a preferred realization of the inventive method, the squeezing means are applied by an endless belt opposite the band-type conveyor and within the area defined by the width of the band-type conveyor, i.e. an endless band is used as the squeezing means, so that the articles conveyed on the band-type conveyor may be squeezed and, if needed, driven to spin around their axis by the endless band opposite to the band-type conveyor. Preferably, the speed of the band-type conveyor and the speed of the endless band acting as the squeezing and spinning means, are independently controlled, so that the speed of article conveyance and the speed of article spinning may be selected independently from each other.
The present invention is further directed to a band conveyor arrangement which, comprises a band-type conveyor with bearing surfaces at predetermined positions for cylindrical articles to be conveyed and with a squeezing arrangement adjacent the band-type conveyor to squeeze the articles toward the band-type conveyor, so as to prevent the articles from leaving the bearing on an acceleration. To overcome the aforementioned disadvantage of the known conveyor arrangement of U.S. Pat. No. 3,310,431 in the band-type conveyor arrangement is improved according to the invention the squeezing means of the conveyor arrangement are arranged opposite the width-extent of the band-type conveyor, so as to directly squeeze the articles towards the band-type conveyor.
The present invention is further directed to a method for applying a coating to at least one surface of cylindrical articles, which method comprises conveying said articles in a predetermined sequence on a band-type conveyor to a coating station, and squeezing said articles between a squeezing arrangement and said bearing surfaces on said band-type conveyor. Such a method is again known from the U.S. Pat. No. 3,310,431, according to which the electrical components are laterally squeezed and conveyed through a coating station at which these components are outside coated.
From the U.S. Pat. No. 3,521,598, a method for inside coating rapidly spinning can bodies is known, according to which the cans are conveyed on an indexing wheel where they are held in semi-tubular indexing bearing surfaces. During the coating operation which occurs as the articles, namely the tubular bodies, are on the indexing wheel, the indexing wheel is stopped and a friction wheel frictionally contacts the tubular body to drive it for spinning. Such a method necessitates not only an exact positioning of respective tubular bodies for inside coating, but especially an exact positioning of the friction wheel, so that said wheel will exactly contact the respective tubular body at a predetermined area of its periphery at exactly the coating position for such a body. Moreover, the time span during which the indexing wheel must stop, is not only determined by the time span of spray coating, but also by the time span necessitated to move the friction wheel in frictional contact with the tubular body, to accelerate the tubular body to the desired spinning speed and then for retraction of the frictional wheel.
By the Japanese patent publication no. 46-32352 there is known a method for outside or inside spraying of tubular bodies on a band-type conveyor, in which a spinning action is imparted to the tubular articles by means of a driving frictional cones contacting the tubular bodies at their outside. The tubular bodies are not squeezed on the band-type conveyor, but reside rather on roller-like bearing surfaces which are driven, so that the amount of acceleration, be it spinning acceleration or linear band conveyor acceleration, is limited.
The present inventive method for applying a coating departs from the known method according to the U.S. Pat. No. 3,310,431 which has the disadvantages of lateral squeezing and additionally, from the standpoint of component spinning, coating, squeezing and driving the electrical components for spinning action is done on the outside of the components. The disadvantage of squeezing and coating on the same side is overcome by the improved method of the invention by spray coating at least the interior surfaces of the articles, being tubular articles, at the coating station, and squeezing the articles at least during their coating by applying the squeezing arrangement opposite and within an area defined by the width of the band-type conveyor at the outside of the articles. Spinning of the articles around their axis is provided by installing a speed difference between the squeezing arrangement and the band-type conveyor, at least at the coating station. In other words, the invention recognizes that the known method for outside coating is well suited especially for interior surface coating of tubular articles by separation of a surface, at which squeezing and possibly spinning actions occur, from a surface to be coated.
Spray coating techniques for interior surfaces of tubular articles are known e.g. from U.S. Pat. Nos. 4,15,8071; 4,291,640; 4,399,945; and 4,060,052, the disclosures of which are hereby incorporated by reference.
A band-type conveyor for inventive central squeezing according to the invention comprises a band-type conveyor with bearing surfaces at predetermined positions for cylindrical articles to be conveyed, and a squeezing arrangement adjacent the band-type conveyor to squeeze the articles toward the band-type conveyor, so as to prevent the articles from leaving the bearing surfaces on an acceleration, wherein the squeezing means are arranged opposite the width-extent of the band-type conveyor, so as to directly squeeze the articles toward the band-type conveyor.
Further, an apparatus of the invention for applying a coating to at least one surface of cylindrical articles, which apparatus overcomes the disadvantages of an apparatus for coating such articles according to U.S. Pat. No. 3,310,431 with respect to obstructing coating by the squeezing means acting on the same side of the articles, comprises a band-type conveyor with bearing surfaces for rotatably supporting the articles at predetermined positions on the band-type conveyor, a squeezing arrangement adjacent to the band-type conveyor for squeezing the articles between the band-type conveyor and the squeezing arrangement, a coating station comprising at least one spray nozzle, substantially aligned with a position of the axis of the cylindrical articles on the bearing surfaces at the coating station, so as to spray coating material into an interior space of the tubular cylindrical articles, and wherein the squeezing means is arranged at least in the coating station opposite the extent in width of the band-type conveyor.
To apply a coating apparatus as disclosed e.g. in the U.S. Pat. No. 4,158,071 to high-speed production wherein tube-like articles, such as can bodies, have to be coated rapidly in order that the coating process is not the slowest stage in a chain of production stages for such articles, one important problem to be solved is how to rapidly convey the articles to and from the coating station and possibly how to rapidly accelerate these articles to spinning around their axis.
Another important problem to be solved is how to make the line adjustable, so as not to limit a line to a single size of articles. All carousel conveying techniques wherein such articles are first fed to a carousel, then coated thereon, then again removed, as e.g. known from the U.S. Pat. No. 3,521,598, are relatively slow, because beyond other facts, the articles first must be loaded and after coating removed from the carousel.
Further objects and advantages of the present invention will become clear from the following description of preferred embodiments of the present invention.